The present invention relates to the field of coherent light sources.
Coherent fiber optic communication systems, high data rate fiber optic systems, and high frequency systems, sensors and signal processing systems demand highly stable, single-mode, narrow linewidth, and broadband tunable semiconductor laser sources. Conventional tunable laser sources using optical gratings, optical tunable filters, or adjustable external cavities have slow tuning speeds in the milli-second or micro-second range. Also, they have difficulty in attaining single-mode, narrow linewidth and broadband tuning simultaneously. Cleaved coupling cavity semiconductor lasers and multi-electrode laser diodes have undesirable narrow tuning ranges and very poor fabrication reproducibility and manufacturing yields.